Operation 4
Installation and Operation Guide 43
The calculator lists the lengths required for the different sizes of uncoated,
deactivated, fused-silica, restrictor tubing available. Choose the id tubing that
gives the shortest length of at least 0.3 m for most detectors and 0.8 m for
MSDs. In this case 0.18-mm id is the choice, requiring 0.912 m for the ECD
restrictor and 0.824 m for the MSD restrictor.
Table 4 on page 33 shows that in both cases the flow is higher than the
minimum 0.72 mL/min suggested for helium in 0.18-mm id tubing.
Calculate column flow
To find the makeup flow at 280 °C, first find the column flow at 280 °C. The
Flow Calculator software (Figure 20) requires that the output pressure be
entered in psia. Therefore 18.496 psia (3.8 psig) is entered.
The column flow drops to 1.38 mL/min at 280 °C.
Figure 20 Column flow calculation